json解码中的格式化

我对解码有疑问有类似的translations.php

<?php
    define("LNG_T1","sdfjaö");
    define("LNG_T2","õäöüåÕÄÖÜ");
    define("LNG_T3","Русский");
    define("LNG_T4","Українська");
    define("LNG_T5","日本語");
    define("LNG_T6","العربية");
?>

还有另一个php文件

<?php
    function startsWith($haystack, $needle) {
        return !strncmp($haystack, $needle, strlen($needle));
    }
    require_once 'translatsions.php';
    header('Content-type: text/javascript; charset=UTF-8');
    $res = array();
    foreach (get_defined_constants() as $k => $v) {
        if (startsWith($k, "LNG_")) {
            $v = preg_replace('/''/', '&#39;', $v);
            $k = strtolower(substr($k, 4));
            $res[$k] = $v;
        }
    }
?>

echo json_encode（$res，json_PRETTY_PRINT）我想看看json

{
    "t1":"sdfjaö",
    "t2":"õäöüåÕÄÖÜ",
    "t3":"Русский",
    "t4":"Українська",
    "t5":"日本語",
    "t6":"العربية"
}

不是类似json的：

{
    "t1": "sdfja'u00f6",
    "t2": "'u00f5'u00e4'u00f6'u00fc'u00e5'u00d5'u00c4'u00d6'u00dc",
    "t3": "'u0420'u0443'u0441'u0441'u043a'u0438'u0439",
    "t4": "'u0423'u043a'u0440'u0430'u0457'u043d'u0441'u044c'u043a'u0430",
    "t5": "'u65e5'u672c'u8a9e",
    "t6": "'u0627'u0644'u0639'u0631'u0628'u064a'u0629"
}

PHP有这样的通用函数吗？